His driving license was also revoked for three months.
The video, shared on social media by a passenger, showed Nguyen Hai Trieu, 35, using his cellphone to turn on music for entertainment while carrying passengers on the Hanoi-Hai Phong Expressway on Monday.
Traffic police said it was a "serious" act that threatened the lives of passengers. He has admitted his violations.
Car and truck drivers caught using their phones while driving can be fined between VND600,000 ($26) and VND800,000 ($35) and have their license temporarily revoked.
The law was put in place in 2017 after several deadly crashes, including one in October 2014 when a bus driver in the central province of Nghe An killed a family of three on a motorbike. Police found the driver had been talking on his cellphone at the time of the crash.
A 2018 survey conducted by the Vietnamese-German Transport Research Center in Ho Chi Minh City and its neighbor Binh Duong Province found six in every 1,000 drivers were on the phone, either texting or talking with the device pressed against their ears.
More than half of Vietnam’s population of over 90 million have a smartphone. Eight in 10 Vietnamese are projected to have one by 2020.
Road crashes are a leading cause of death in Vietnam, killing almost one person every hour.
More than 18,720 accidents occurred last year, killing 8,244 people and injuring nearly 14,800, according to the National Traffic Safety Committee.